The present invention relates to an apparatus and a method for fuel metering in a motor vehicle.
In motor vehicles having an internal combustion engine, fuel is delivered out of a fuel container with the aid of an electric fuel pump, and conveyed via fuel lines to the injection valves. In internal combustion engines with high-pressure injection, in particular in internal combustion engines with auto-ignition, the electric fuel pump is followed by a further pump which generates a very high pressure in a high-pressure region of the fuel supply system that communicates with the injection valves.
German Patent Application No. 44 40 700 describes a high-pressure fuel injection system in which the acceleration which is detected by a sensor is compared with a defined value which, if exceeded, causes an accident such as a collision to be diagnosed. If the sensed acceleration exceeds the defined value, the pressure in the high-pressure region is sharply reduced, so that in the event of damage to the high-pressure line due to a severe impact, discharge of fuel at high pressure is prevented. The reduction in the high pressure has therefore already started in the time frame of an impact.
Antilock braking control systems per se are known as described, for example, in Bosch Technical Reports, Vol. 7, (1980), No. 2. In such antilock braking systems, the braking systems of the vehicle wheels are activated in such a way that a change in braking effect, generally in braking pressure, occurs as a function of an instability value. This instability value is generated as a function of the detected wheel motion, generally of the wheel rotation. This instability value is, in particular, a combination of the instantaneous wheel circumference deceleration or wheel circumference acceleration and the brake slippage.
Conventional vehicle dynamics control systems include a variable which influences and/or represents the dynamics of the vehicle, for example the yaw angle velocity, the steering angle, and/or the transverse acceleration of the vehicle, is detected. As a function of these detected variables, the braking systems of the wheels are activated so as to increase vehicle stability. Such conventional system is described, for example, in xe2x80x9cBosch FDR vehicle dynamics regulation systemxe2x80x9d (FDR-Fahrdynamikregelung von Bosch), ATZ Automobiltechnisches Zeitschrift 96 (1994).
It is the object of the present invention to eliminate, in reliable and cost-effective fashion, the danger of fuel discharge under high pressure.
The present invention relates to a system for fuel metering in a motor vehicle in which the fuel in a reservoir has a definable pressure. According to the present invention, a means (or a system) for reducing the pressure and a further means (or another system) for issuing a signal relevant to vehicle safety are provided. In this context, the pressure is reduced in reaction to the signal relevant to vehicle safety.
The present invention provides the means for issuing the signal relevant to vehicle safety that are configured in such a way that, in order to increase vehicle stability, the braking effect can be modified via at least one vehicle wheel brake, the signal relevant to vehicle safety being issued as a function of a definable modification of braking effect.
The present invention is based on the fact that the safety systems which affect the vehicle brakes go into action prior to a possible accident or a possible collision in which the high-pressure portion of the fuel delivery system might in some circumstances be damaged. If the fuel pressure is decreased as a function of such brake actions, the result is a relatively early safety-related reduction in fuel pressure. An engine torque reduction possibly associated with the pressure reduction is of little relevance in this context. In addition, the pressure reduction can be actuated, within certain limits, in such a way that no substantial reduction in engine torque occurs. For this purpose, for example, the fuel injection duration can be extended as the pressure is reduced.
In modern motor vehicle systems, the engine control device is generally connected by using a bus system to the antilock or vehicle dynamics control device which acts on the brakes. An essential advantage of the present invention is the fact that the safety advantage achieved by the present invention can be attained solely by using a specific software intervention that can be implemented relatively economically.
In an advantageous embodiment of the present invention, second means can be configured as an antilock braking system (ABS), in which any incipient locking of a vehicle wheel is detected. In antilock braking systems, the braking effect at the wheel is modified, in response to a detection of incipient locking of a definable magnitude, in such a way that the braking effect is kept constant or is reduced. In this embodiment of the present invention, provision is made for the signal relevant to vehicle safety to be issued as a function of that modification. In this embodiment, therefore, the fuel pressure can be reduced when incipient locking is detected, i.e. at the onset of active ABS control operation.
In an ABS system, wheel slippage and/or wheel deceleration are generally determined at least as a function of detected wheel rotation velocities. To detect incipient locking, the determined wheel slippage and/or determined wheel deceleration are compared with threshold values.
In a further embodiment of the present invention, the second means to be configured as a vehicle dynamics control system (FDR), in which the yaw behavior and/or transverse motion behavior of the vehicle are detected and compared with specific setpoints and/or reference profiles. In this context, when a deviation of a certain magnitude between the detected behavior and the pertinent reference profile is recognized, the braking effect at particular wheels is modified in such a way that the deviation is minimized. In this case the signal relevant to vehicle safety is issued as a function of the modification.
With such FDR systems, provision is generally made for the setpoints and/or reference profiles to be determined at least as a function of the detected longitudinal vehicle speed and the detected steering movement.
The aforesaid modifications of the braking effect can be implemented by changing the brake pressure in the wheel brakes, or by means of a brake actuated by an electric motor.
The subject of the present invention includes a method for fuel metering in a motor vehicle in which the fuel in a reservoir has a definable pressure, such that a signal relevant to vehicle safety is issued and the pressure is reduced in reaction to the signal relevant to vehicle safety. The method according to the present invention provides that in order to increase vehicle stability, the braking effect at least one vehicle wheel brake can be modified, and the signal relevant to vehicle safety is issued as a function of a definable modification of braking effect.